Antibodies specific for the purine and pyrimidine bases of nucleic acids may be obtained using nucleoside- or nucleotide-protein conjugates. Such antibodies react with denatured DNA and with RNA. The objectives of the proposed research are to delineate the utility of these antibodies for immunochemical and biochemical investigations of nucleic acids. Among the studies being pursued are: a) To prepare antibodies specific for oligonucleotide sequences. b) To prepare nucleic acid-reactive antibodies as homogeneous proteins in order to study relationships of structure to specificity. c) To study antibodies specific for 7-methylguanosine phosphate and to examine its reaction with messenger RNA. d) To use immunochemical procedures to probe the structure of metaphase chromosomes. e) To develop a procedure for studying the secretion of macromolecules by single cells and detection of immunoglobulin-secreting cells.